Alcohol, sodium sensitivity and blood pressure

New research indicates that withdrawal from heavy drinking may derange sodium metabolism in such a way that a person’s sodium sensitivity is increased, leading to higher blood pressure.

Alcohol appears to have the potential for both beneficial and toxic effects on the heart. The "French Paradox," for example, refers to the protective properties that red wine may have vis-à-vis heart disease. Chronic heavy drinking, on the other hand, is a leading cause of several cardiovascular illnesses, including high blood pressure. High blood pressure, or hypertension, increases the risk for heart disease and stroke, both leading causes of death in the United States. A study in the December issue of Alcoholism: Clinical & Experimental Research has found that alcohol-induced sodium sensitivity may be one of the mechanisms underlying the association among heavy alcohol consumption, alcohol withdrawal, and high blood pressure.

"We know that chronic exposure to heavy amounts of alcohol elevates blood pressure and contributes to hypertension among alcoholics," said Cristiana Di Gennaro, a junior scientist at the University of Parma and corresponding author for the study. "We also know that sodium sensitivity is characterized by an increase of blood pressure, although not necessarily in the hypertensive range, when salt intake is elevated. In addition, sodium sensitivity has been shown to be an independent risk factor for cardiovascular disease. Our findings indicate that alcohol consumption may raise blood pressure through the induction of a sodium sensitive state."

"There is some evidence that for heavy drinkers, even when they don’t drink, blood pressure is high," said Maurizio Trevisan, professor and chairman of the department of social and preventive medicine at the School of Medicine, University of Buffalo. "The day after they drink, for example, their blood pressure may be higher than normal. If they drink chronically, they are in sort of a constant level of withdrawal. This can occur even in people that drink normally, moderate drinkers, although the evidence is not as clear as it is for the heavy drinkers." What happens during these "mini-withdrawals," he said, is even more pronounced during extended or complete withdrawal.

Researchers examined 18 alcoholics (6 females, 12 males) entering in-hospital detoxification at the University of Parma in Italy. Their blood pressure and sodium levels were assessed during their first eight days of stay. During this time, each patient was on a fixed hospital diet that provided 150 mM of sodium per day (considered ‘normal’). After one year of carefully monitored abstinence, study participants underwent a four-week phase of examination, which included measuring their blood pressure levels on three separate occasions. Then they were asked to adhere to a diet of 55 mM of sodium per day (considered ‘low’), which was later supplemented with 205 mM (for a total of 260 mM, considered ‘high’) of sodium per day.

During the first eight days of withdrawal, alcoholics on a ‘normal’ diet of sodium intake nonetheless demonstrated high sodium levels, weight gain, and increased blood pressure. A year later, and during exposure to the dietary sodium manipulations, the same group displayed much more significant changes in blood pressure and greater sodium sensitivity when compared to a group of teetotalers. In addition, changes in blood pressure during the early withdrawal period were related to sodium sensitivity during long-term abstinence. These findings suggest that salt sensitivity plays a key role in blood pressure regulation in early withdrawing alcoholics.

"Prior to this study," said Trevisan, "we knew about some of the conditions that increase sodium sensitivity. One of them is insulin resistance, another is being overweight. Now we have [yet] another factor that appears to increase someone’s sodium sensitivity, that is, heavy alcohol consumption. It looks like heavy alcohol consumption for long periods of time appears to derange your sodium metabolism in a way that makes you more sodium sensitive."

"We do not know definitely whether sodium sensitivity is an acquired trait linked to alcohol abuse," added Di Gennaro, "or a genetic trait. "We do know, however, that sodium sensitivity remains significant after at least one year of alcohol abstinence in heavy alcoholics. We believe that our demonstration of an important interaction among alcohol consumption, sodium metabolism, blood pressure regulation and cardiovascular diseases extends further our knowledge about the impact of dietary and lifestyle factors on one of the most important causes of morbidity and mortality in western countries. Our findings also suggest that a dietary reduction of both alcohol and salt is warranted."

Trevisan agrees. "Everybody should benefit from a low-sodium diet anyway," he said.

Funding for this Addiction Science Made Easy project is provided by the Addiction Technology Transfer Center National Office, under the cooperative agreement from the Center for Substance Abuse Treatment of SAMHSA.